Composition, digestibility and utilization of endophyte-free tall fescue fed as green-chop or hay to sheep

Abstract

Two lamb digestion trials were conducted using three cultivars of endophyte-free tall fescue ( Festuca arundinacea Schreb.) that had been harvested from paddocks as green-chop forage of initial growth or as regrowth hay. The tall fescue cultivars were Johnstone (JOHN), AU Triumph (AUT) and Kentucky 31 (KY-31). All cultivars within each harvesting method contained similar quantities of dry matter (DM) and organic matter (OM). Both JOHN green-chop and hay contained more crude protein (CP) than the corresponding harvest of AUT or KY-31. Green-chop JOHN contained less ( P < 0.10) acid detergent fiber (ADF) and neutral detergent fiber (NDF), whereas JOHN hay contained more ADF and NDF than AUT or KY-31. The DM, OM, CP, ADF and NDF of JOHN green-chop were more digestible ( P < 0.10) than KY-31 or AUT. The same trend existed for hay, but digestibility of OM and CP did not differ between John and KY-31. The DM, OM, ADF and NDF digestibilities of AUT were greater ( P < 0.10) than KY-31 when harvested as green-chop forage and fed to lambs. No differences in digestibilities of DM, OM, N, ADF or NDF of AUT and KY-31 were observed when fed as hay. Ingestion and excretion of N were greater ( P < 0.10) in both trials for lambs fed JOHN. However, N retention was similar for all lambs except for reduced ( P < 0.05) N retention by lambs fed KY-31 green-chop forage. It can be inferred from these results that the DM, OM, ADF and NDF contents of Johnstone tall fescue are more digestible than Kentucky-31 or AU Triumph when fed to sheep as hay or green-chop forage when harvested in a vegetative stage.